TY - GEN
T1 - Graphite thermal neutron scattering cross section calculations including coherent 1-phonon effects
AU - Hawari, Ayman I.
AU - Al-Qasir, Iyad I.
PY - 2008
Y1 - 2008
N2 - Graphite serves as the moderator and reflector for the very high temperature (VHTR) concepts that are currently under study as part of the proposed Generation IV reactors. The VHTR is a "thermal" reactor where, to propagate the chain reaction, neutrons born in fission slow-down and thermalize in the graphite moderator prior to initiating a new fission reaction. Consequently, accurate quantification of the thermalization phenomenon using thermal scattering cross sections enhances the ability to predict the thermal neutron spectrum in the core. For graphite, which is characterized by a strong coherent scattering behaviour, deviations have been observed between thermal neutron scattering cross sections that are calculated using the incoherent approximation and total cross section values measured using pyrolytic graphite samples. These deviations are remedied by accounting for the coherent 1-phonon component of the cross section. However, discrepancies remain with total cross section values that are measured using reactor grade graphite samples. In this case, the discrepancies are attributed to differences between the actual structure of reactor grade graphite and the structure assumed in the lattice dynamics model that is implemented in typical cross section calculations.
AB - Graphite serves as the moderator and reflector for the very high temperature (VHTR) concepts that are currently under study as part of the proposed Generation IV reactors. The VHTR is a "thermal" reactor where, to propagate the chain reaction, neutrons born in fission slow-down and thermalize in the graphite moderator prior to initiating a new fission reaction. Consequently, accurate quantification of the thermalization phenomenon using thermal scattering cross sections enhances the ability to predict the thermal neutron spectrum in the core. For graphite, which is characterized by a strong coherent scattering behaviour, deviations have been observed between thermal neutron scattering cross sections that are calculated using the incoherent approximation and total cross section values measured using pyrolytic graphite samples. These deviations are remedied by accounting for the coherent 1-phonon component of the cross section. However, discrepancies remain with total cross section values that are measured using reactor grade graphite samples. In this case, the discrepancies are attributed to differences between the actual structure of reactor grade graphite and the structure assumed in the lattice dynamics model that is implemented in typical cross section calculations.
UR - http://www.scopus.com/inward/record.url?scp=79953841459&partnerID=8YFLogxK
M3 - Conference contribution
AN - SCOPUS:79953841459
SN - 9781617821219
T3 - International Conference on the Physics of Reactors 2008, PHYSOR 08
SP - 347
EP - 353
BT - International Conference on the Physics of Reactors 2008, PHYSOR 08
PB - Paul Scherrer Institut
T2 - International Conference on the Physics of Reactors 2008, PHYSOR 08
Y2 - 14 September 2008 through 19 September 2008
ER -